National Source Water (Untreated) Levels of GiardiaFEBRUARY 1998

REMINDER: Data Purpose: The ICR data were collected as part of a national research project to support development
of national drinking water standards. They should NOT be used to determine local water systems compliance with drinking water standards, nor should they
be used to make personal judgements about health risks.

Results of Zero: A measurement of zero means that no Giardia was found in the sample volume that was analyzed.
Zero results do not indicate the absence of Giardia in the source water because the method recovery is low and the amount of sample analyzed is small.
In other words, Giardia may be present in source water even if no cysts are counted for the sample volume analyzed.
The presence of Giardia may also be mistakenly identified as other organic material such as algae.

Efforts Beyond Regulations: Many large public water systems are voluntarily improving the control of pathogens by participating in the Partnership for Safe Water, an initiative between EPA,
the States, and water suppliers to improve the performance of treatment.

Percent Treatment Plants Reporting a Positive Occurrence of Giardia

* A measurement result of zero means that no cysts were found in the volume of water analyzed.